I did not pass smog due to the amount measured for the hc [ppm] test read to high it reads at 711 at 15 mph and 767 at 25 mph what can i do to fix this?

wow, no context but i can read your mind?
ok SMOG failed. right?
what speed, there are 2 in uSA, 15 and 25.mph.
so there are 3 tests, which one. all are PPM in usa.
parts per million.
but is that HC , CO, or NOX? or ?

based on your numbers is HC
hydrocarbons or in barstool, its raw gasoline leaving rear of car.
unburned fuel..

572 ppm is way too high 12-19 is normal
id say the CAT is bad.
but can be , engine is bad, and burned out the cat.
that is why all savvy mechanics, check the that the engines
holds closed loop status, (EFI closed loop) at the speed yours failed.
if not in closed loop the cat will burn up (rich)
that is first.
Once that is cured. you check HC again. if out of spec
you did burn up the can , new cat time.

that is the correct way.

Emission test by codes reader? or smog? Any codes?

fist i would like you to post the year make and model of the truck along with the HC ppms and NOX ppm it would be very helpful but high hc and nox can be attributed to a faulty EGR system nox is produced when the combustion chamber temperature gets too high so a small amount of exhaust is cycled back into the air stream to help cool them there are other causes but without looking at the levels its much harder to say

Hi Larry, I your position I believe I would take the vehicle for a diagnostic scan and then check the read outs. There could be a problem with any one of a number of sensors but I believe you'll end up with all odds pointing at the cat. Regards John

the smog test looks like the engine is miss firing, that could cause the timing to be out of whack also, try a old fashioned tune up, new spark plugs, wires, and filters also replace the PCV valve. any time you see the NO that high suspect a miss fire.

High HC means moisture in the system. Try driving it longer then take it to the smog shop. Otherwise it could be hard like a head gasket or easy such as a PCV not functioning. Any ways you should always drive it about 20 miles before smog check, longer when the weather is cold.

An old worn out engine will have high emmisions due to burning oil. Also, with age, a catalitic converter won't burn up any fuel vapors causing high emmisions.

You did not post the odometer reading on the van but base on the year it should has over 85,000+ miles on it.

The most likely source of the high Hydrocarbon (HC) is clogged or drippy injectors.

Change the fuel filter if it is over 48K miles.

Ran two or more tanks full of Chevron gas will help clean out the fuel system.

====

The air fuel ratio can be off is the air filter is clogged or the mass air flow sensor give incorrect data to the computer (ECU).

Change the air filter is it over 20,000 miles or you can see sunlight though it.

Use CRC Mass Air Flow cleaner or electronic part clean to gently clean the mass air flow sensor.

==========

Change the oil to 20W50 or one grade higher to prevent blow by.

You current motor oil is soak with HC from blow by.

=======

Make sure the tires are at 32 psi

=======

Do the smog test is a COLD morning?

=======

REMOVE excess cargo off the van.

=======

These are little things that I would do.

If the HC is still high at 25 mph then you will need a professional fuel injector cleaning or replace the injectors.


Please post more data on the third smog test on the comment window.

have you had the the engine codes pulled and reset?
and if so what are your engine codes?
i dont know of any car that will pass emissions test with the engine light on.
we cure your trouble that caused your engine light to come on and you will pass your test.
later
paul

Do an oil change with 20W50 oil (or one grade higher) to prevent blow by during the test.

You current oil has HC from blow by though the rings.

Do a fresh oil change will lower the HC.

========
Change spark plugs,wires,cap and rotor if they are over 24,000 miles
========

Make the smog check appointment for the EARLY MORNING. Colder air will help the fuel burn better.

========

Clean or change the air filter and pcv valve.

Clean Mass Air Flow sensor with CRC Mass Air flow cleaner or electronic part cleaner.

========

Do a quick wipe down on the wires and cap to take the moisture off.

========

Check spark plug wire contacts for corrosion.

========

Fill the tank to around 3/4.......just in case your fuel pump is weak.

========

Ran the truck for 20+ minutes on highway before the test.

========

Do not carry excessive cargo on the truck bed.


These are the little things I would do to get the HC and CO down.


Please post more information on the comment window.